(1)Field of the Invention
The present invention concerns a cutting head having a cutting oxygen axial duct and a plurality of coaxial ducts of oxycombustible mixture connected upstream to an annular distribution chamber of combustible mixture.
(2)Description of Prior Art
Generally, a cutting head of this type is produced by means of a central cutting member or nozzle having a cutting oxygen axial duct, a plurality of longitudinal ribs on at least a portion of its longitudinal portion, this member being mounted, typically by means of a screw, in an external sheath defining with said ribs said plurality of ducts of oxycombustible mixture.
These known cutting heads have a certain number of disadvantages, for example:
Taking into account the size of the cutting heads (about 50 to 60 mm of axial length), the production of a cutting duct is delicate in as much as this cutting duct has a converging section followed by a collar and a diverging section and that the machining of a converging section, a sonic collar and a diverging section constitute a determining element to give good performances.
The known devices are such that the upstream end of the member incorporating the cutting head covers the sheath end, so that to allow the oxycombustible mixture to pass into the intermediate distribution chamber, it is necessary to provide connecting perforations through this cover.
Sealing of the parts constituting the torch head on the one hand and between head and torch body on the other hand, is difficult to maintain since the degrees of sealing are reduced because of the existence of an annular distribution channel in the upstream end face of the internal member.
Because of the presence of an annular distribution chamber of oxycombustible mixture between the cutting nozzle and the sheath, it is essential that these heads be dismantlable, since when cleaning them after use, small particles of oxides can be introduced inside them and disturb the gaseous flow. On the other hand, this design does not promote the removal of the calories which have been absorbed by the head during a cutting operation.
The cost of these cutting heads is relatively high in starting material and machining in view of their large dimension and the perforations required for feeding an oxycombustible mixture.
The present invention aims at a new head design enabling to solve the problems exposed above, while preserving and even improving operational performances and ensuring to the material an excellent industrial reliability.